Capacitive touchpads or keypads that include a layer of semi-conductive material are known, and find widespread use in mobile electronic devices. When using a capacitive sensor in impedance measurement configuration in a there is always a need for a sheet or layer of semi-conductive material. Making good connections to this semi-conductive material is difficult, as soldering is most often not possible, and wiring is always hard and expensive. Previous solutions used a paper sheet or ITO that has a certain square-resistance, suitable for the impedance based capacitive sensing usage. The problem is related to this construction is the problem of making reliable connections from the paper sheet to the electronics. Attaching wires is difficult, as the materials cannot tolerate heat (for soldering), and silver paste is not very robust in use.
Also, thinness of keypads and touchpads is a crucial factor in the modern mobile device business.